Density Demonstration (00:06:23)[30-Sep-09] This activity demonstrates that fluids arrange into layers according to their densities. The two "water masses" - salt (blue) vs. fresh (yellow), or cold (blue) vs. warm (yellow) - are initially separated by the tank's divider. When the divider is removed, the denser water (salt water or cold water [blue]) sinks to the bottom of the container and the less-dense water (fresh or warm water [yellow]) floats above, forming a stratified column. In the process, an internal wave is formed in the tank. Credit: Karp-Boss, L., E. Boss, H. Weller, J. Loftin, and J. Albright. 2009. Teaching Physical Concepts in Oceanography: An Inquiry Based Approach. Oceanography 22(3), supplement, 48 pp, http://dx.doi.org/10.5670/oceanog.2009.supplement.01.
Original Movie: http://tos.org/hands-on/teaching_phys.html